The present invention relates to a thermal development apparatus and an image recording apparatus utilizing the thermal developing apparatus.
1. Prior Art
In an image recording apparatus such as a laser imager, image data input from a medical imaging device such as a radiographing apparatus and MRI are subjected to an image processing such as a gradation processing, and a heat development film (referred to as film hereinafter) is scanned by a laser beam based on the image data having been subjected to image processing to form a latent image on the film. After that, the film on which a latent image is formed is heated and developed to record a visible image on the film.
A thermal developing apparatus heats the film and conducts development by transporting the film in close contact to the outer peripheral surface of a drum-shaped heating section of the apparatus. Herein, in order to obtain a high quality image, it is necessary to ensure stable close contact of the film with the heating section. To achieve this, plural pressing rollers are arranged parallel to each other along the outer peripheral surface of the heating section with a prescribed pitch, and the film is transported with a condition of being nipped between the pressing rollers and the heating section. During this, the film is made in close contact with the peripheral surface of the heating section due to being pressed by the pressing rollers.
Further, in the image recording apparatus, in order to compensate for image quality fluctuation caused by ambient environmental fluctuation, and aged deterioration of the image recording apparatus and the film, etc., in the course of forming a latent image on the film a prescribed amount of laser is irradiated on a part of the film to form a compensation standard area (a density patch). The image recording apparatus measures the density of the density patch area after development by the thermal development apparatus, compensates image data to be used for forming the next latent images, and determines laser irradiation amount, based on the measured density and the predetermined target density of the density patch.
2. Problems to be Solved by the Invention
In cases where the film is transported under close contact with the outer peripheral surface of the heating section, almost all portions of the film are pressed by the pressing rollers to form a stable contact condition, however, at the leading edge portion and the trailing edge portion the contact becomes unstable because edges of the films are not pressed all the time by the pressing rollers. For this reason, the film flip-flops at the top end portion and the trailing edge portion depending on the peripheral surface curvature of the heating section and the inherent elastic force of the film. In cases where the film flip-flops, the film may float up from the peripheral surface of the heating section and may not receive sufficient heat for development, resulting in degradation or fluctuation of the density as generated as shown in FIG. 5. These unstable areas extend into the effective image area that is necessary for diagnosis and the like, and the area that can be actually used for diagnosis is narrowed.
Incidentally, if the density patch N is positioned inside the effective image area, the diagnosis can possibly be disturbed by the density patch N, therefore, the density patch is usually provided outside the effective image area. However, if the density patch N is provided at the leading edge portion or trailing edge portion of the film, due to the above-explained flip-flops of the film, the density of the density patch itself can be degraded or fluctuate. When the density of the density patch whose density is unstable is measured, correct compensation can not be conducted, and as a result, the finishing quality of the film F to be image recorded thereafter will worsen and image quality in the effective image area will also fluctuate.
Objectives of the present invention are to provide a heat developing apparatus and an image recording apparatus that suppress degradation and fluctuation of the image quality in the effective image area.
The objectives of the present invention can be attained by the following structures.
(1) A thermal development apparatus for developing a film for thermal development, comprising:
a heating section, which has at least a partially cylindrical surface at an outer peripheral portion of the heating section, for transporting the film while heating the film being brought into contact with the partially cylindrical surface;
a plurality of pressing rollers provided in parallel with each other along with a transportation path of the film, which is transported along the partially cylindrical surface of the heating section, for pressing the film onto the partially cylindrical surface of the heating section;
wherein when xe2x80x9cRxe2x80x9d denotes the curvature radius of the partially cylindrical surface, xe2x80x9crxe2x80x9d denotes the radius of each of the plurality of pressing rollers, xe2x80x9cxcex1 (degrees)xe2x80x9d denotes an angle between two neighboring axial centers of the plurality of pressing rollers with respect to the center of the curvature radius of the partially cylindrical surface, and xe2x80x9cPxe2x80x9d denotes the pitch with which the plurality of pressing rollers are provided; the following expressions are satisfied;
P=2xcfx80Rxcex1/360, 
P greater than 2r 
wherein, when xe2x80x9clxe2x80x9d denotes the shortest distance between the leading or trailing edge of the effective image area recorded on the film and the leading or the trailing edge of the film; the relationship of l greater than P is satisfied.
According to the structure (1), since the radius xe2x80x9crxe2x80x9d, the angle xe2x80x9cxcex1xe2x80x9d, and the pitch xe2x80x9cPxe2x80x9d are established such that xe2x80x9cl greater than Pxe2x80x9d is satisfied, even if the leading edge portion or the trailing edge portion of the film flip-flops during the development process, at least the effective image area is effectively pressed by the pressing rollers onto the outer peripheral surface of the heating section. Therefore, in the development process the effective image area can be stably provided heat to prevent the deterioration or fluctuation density areas from encroaching into the effective image area, and image quality degradation or fluctuation can be reduced.
(2) The thermal development apparatus according to the structure (1), characterized in that the surface material of the plurality of pressing rollers is comprised of rubber or a rubber-like material.
According to the structure (2), since the surface material of the plurality of pressing rollers is comprised of rubber or a rubber-like material, when the pressing rollers press the film for thermal development onto the partially cylindrical peripheral surface of the heating section, the surface material of the pressing rollers elastically deforms to make area-contacts of the film with the partially cylindrical peripheral surface. In the case of line-contact of the two, since the film is pressed at lines, the leading edge and the trailing edge portion are apt to flip-flop. However in the case of structure (2), since the film and the heating section are brought into area-contact, the flip-flops at the leading edge and the trailing edge portion can be suppressed.
Further, in cases where the surface material of the pressing rollers is elastically deformed, the distance between neighboring pressed areas is reduced to shorter than the predetermined pitch, and an area broader than the effective image area can be pressed onto the outer peripheral surface of the heating section. By this action, the degradation or fluctuation of the image quality can be suppressed in an area broader than the effective image area.
(3) The thermal development apparatus according to the structure (2), characterized in that hardness (JIS-A) of the surface material of the plurality of pressing rollers is in the range of 20 to 60 degrees.
If the hardness of the surface material is greater than 60 degrees, since it does not sufficiently deform and contacting area of the material onto the film is restricted to small, it is not easy to suppress the flip-flops at the leading edge and trailing edge portion of the film. In the present invention, hardness (JIS-A) of the surface material of the plurality of pressing rollers is in the range of 20 to 60 degrees, therefore, the surface material effectively deforms to suppress the flip-flops at the leading edge and trailing edge portion of the film.
(4) An image recording apparatus comprising:
a laser scanning apparatus for forming a latent image on a film for thermal development by scanning the film with a laser beam; and
a thermal development apparatus for developing the latent image formed on the film by heating the film;
wherein in the course of forming the latent image, the laser scanning apparatus forms a compensation standard area at a prescribed position on the film by irradiating the film with a prescribed amount of laser irradiation,
wherein the thermal developing apparatus comprises:
a heating section, which has at least a partially cylindrical surface at an outer peripheral portion of the heating section, for transporting and heating the film while the film being brought into contact with the partially cylindrical surface;
a plurality of pressing rollers provided in parallel with each other along the transportation path of the film, which is transported along the partially cylindrical surface of the heating section, for pressing the film onto the partially cylindrical surface of the heating section;
wherein when xe2x80x9cRxe2x80x9d denotes the curvature radius of the partially cylindrical surface, xe2x80x9crxe2x80x9d denotes the radius of each of the plurality of pressing rollers, xe2x80x9cxcex1 (degrees)xe2x80x9d denotes the angle between two neighboring axial centers of the plurality of pressing rollers with respect to the center of the curvature radius of the partially cylindrical surface, and xe2x80x9cPxe2x80x9d denotes the pitch with which the plurality of pressing rollers are provided; the following expressions are satisfied;
P=2xcfx80Rxcex1/360, 
P greater than 2r 
wherein, when xe2x80x9cLxe2x80x9d denotes the shortest distance between the leading or trailing edge of the compensation standard area formed on the film and the leading or the trailing edge of the film; the relation of L greater than P is satisfied.
According to the structure (4), since the radius xe2x80x9crxe2x80x9d, the angle xe2x80x9cxcex1xe2x80x9d, and the pitch xe2x80x9cPxe2x80x9d are established such that xe2x80x9cL greater than Pxe2x80x9d is satisfied, even if the leading edge portion or the trailing edge portion of the film flip-flops during the development process, the compensation standard area is pressed by the pressing rollers onto the peripheral surface of the heating section. Therefore, in the development process the compensation standard area can be stably provided heat to prevent deteriorated or fluctuated density areas caused by the flip-flops from encroaching into the compensation standard area. Therefore, the compensation standard area after development shows stable density, and by conducting compensation based on this stable density, the finishing quality of images on the film to be subsequently recorded can be stablilized and degradation and fluctuation of the image quality in the effective image area can be suppressed.
(5) The image recording apparatus according to the structure (4), further comprises a density measurement device for measuring the density at the compensation standard area, and the image recording apparatus compensates the amount of laser irradiation based on the difference between the measured density by the density measurement device and the target density of the compensation standard area.
According to the structure (5), since the amount of laser irradiation is compensated based on the difference between the measured density by the density measurement device and the target density of the compensation standard area, the compensation relating to environmental fluctuation and aged deterioration of the image recording apparatus or the film can be stably performed.